Find out how O2 can be a key element of a good workout.

Inhale. Exhale.

Sounds pretty simple, right? But if you do it wrong during a workout you can deprive muscles of oxygen and wear yourself out. Learn the ins and outs of breathing new life into your routine:

Strength training and push-ups

In: The rule of thumb is to exhale while contracting muscles (when you lift the weight or push up), and inhale while releasing.
Out: Careful not to exhale (and release) too quickly. Remind yourself to slow down by making a long sound while exhaling.

Crunches

In: On your way up, breathe out as much as you can. At the top, when your muscles are contracted, breathe in and out, then inhale on the way down.
Out: Don't hold your breath--it'll minimize the effect on your muscles. If the above pattern is too hard, try this simple crunch technique.

Running and other cardio

In: They key is breathe deeply and consistently (shallow, quick breathing increases heart rate, which decreases endurance). For a consistent pattern, synch your breathing to music.
Out: Don't breathe solely with your mouth--watch this video for tips on alternating nose and mouth.